title: Scaffolding function of PAK in the PDK1-Akt pathway.
abstract: Many extracellular signals stimulate phosphatidylinositol-3-kinase, which in turn activates the Rac1 GTPase, the protein kinase Akt and the Akt Thr 308 upstream kinase PDK1. Active Rac1 stimulates a number of events, including substrate phosphorylation by a subgroup of the PAK family of kinases. The combined effects of Rac1, PDK1 and Akt are crucial for cell migration, growth, survival, metabolism and tumorigenesis. Here we show that Rac1 stimulates a second, kinase-independent function of PAK1. The PAK1 kinase domain serves as a scaffold to facilitate Akt stimulation by PDK1 and to aid recruitment of Akt to the membrane. PAK differentially activates subpopulations of Akt. These findings reveal scaffolding functions of PAK that regulate the efficiency, localization and specificity of the PDK1-Akt pathway.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Higuchi
authors.forename: Keisuke
authors.initials: K
authors.lastname: Onishi
authors.forename: Chikako
authors.initials: C
authors.lastname: Kikuchi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Gotoh
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology; D005982:Glutathione Transferase / Q000378:metabolism; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010957:Plasmids; D011494:Protein Kinases / Q000378:metabolism / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D034622:RNA Interference; D051381:Rats; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D054462:p21-Activated Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology
chemical_list: D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011994:Recombinant Proteins; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein; C000631433:Pdk1 protein, mouse; C000631434:Pdk1 protein, rat